An ion milling device is a device performing thin film processing and cross-section processing of a sample or the like serving as an observation object for a scanning electron microscope or a transmission electron microscope and processes the sample such as a metal, glass, and a ceramic by irradiating the sample with a beam such as argon ion beam. Such processing is performed in a vacuum chamber.
Meanwhile, the temperature of the sample increases by ion beam irradiation. Since the sample may be damaged when the temperature of the sample increases excessively, known is a method for connecting a sample stage to a cooling source such as a Peltier element and cooling the sample to prevent the sample from being damaged, as disclosed in PTL 1. PTL 1 also discloses a method for inverting current to be supplied to the Peltier element to heat the sample in order to suppress frost or condensation occurring at atmospheric release of the vacuum chamber of the ion milling device.